Metal alloys and processes of making the same



Feb. 9, 1937. G. E. sEIL METAL ALLOYS AND PROCESSES OF MAKING THE-SAMEFiled Jan. 18, 1936 2 Sheets-Shea?l l :Snventor GILBERT E. SEIL(Ittorneg Feb. 9, 1937. G, E. sElL METAL ALLOYS AND PROCESSES OF MAKINGTHE SAME Filed Jan. 18, 1936 2 Sheets-Sheet 2 mn?, mE ws 3E l R E B L G,i

Gttorneg Patented heb., 9, 1937 f Marat. .enters raoocsses or e 'run sYon-lf.

amputation .tamtam is, icas, semi No. 59,69@ lin @a August i9, 1935 9Cla.

A This invention relates to therening of metals, metallic material, ormetal alloys. More particularly, it deals with the control of theultimate content of desirable and undesirable constituents of metals andmetal alloys, and the scope of the invention is broad enough to containWithin its purview not only novel processes, but products resulting frompracticing such processes and possibly furnace structures in which suchprocesses can be carried out.

The general object of this invention is to refine metallic materialand/or metal alloys especially those containing adesirable constituentsuch as chromium, in a simple and readily controlled manner by whichthere is facilitated, to an exselective oxidation thereof. I

Another object of this invention is to bring labout this oxidation ofimpurities under conditions as nearly ideal therefor 'as possible'bothas to speed of reaction and eiciency thereof, Anamely with the reactivematerials in miscible solution and thoroughly mingled. A further objectis to carry out this reacting of materials in solution in the presenceof a carbon monoxide superatmospheric pressure to assure absence of air.

And a further very important object of the invention is to form in aheated reaction zone and exteriorly ofthe bath of metallic material tobe refined, a highly concentrated oxidizing reagent for use in refiningsuch metallic material. With respect to this reagent whose oxidizingcomponent is a metal-oxide, an object is to effect first the reductionof a quantity of the'metal oxide (which may be in the form of ore) intometal, and second the dissolution in the thus formed metal as a solvent,o a quantity of the oxide present. Another object is to contact globulesof the metal solvent With the oxide solute whereby there is exposed tothe oxide surrounding the metal globules, abnormally large surfaces' perunit of weightfor thus facilitating the dissolving of the oxide in themetal. And a further object of this invention is to retain or confineand prolong close contact of the reagent forming materials in thereaction zone suiiiciently for the mass of material to be forced totemperatures (l) above which the reducing reactiontakes place to convertsome of the metal oxide to metal, and 2) above the melting point of themetal at which the solubility of the oxide in the metal increases to apointI where a substantial quantity of the oxide goes into solution Vin.the metal. To this end, another object is to vary in some easy mannerthe ratios or proportions of the reactive and l slag forming componentsin the zone where the reagent is formed. Still another object is toproduce a metal refining oxidizing reagent which can bel sold as suchand for other purposes. A still further 4Vobject is to correct the bathso that when the oxidizing reagent is added to the bath, the reagentwill selectively oxidize the carbon or other oxidizable impurity in thebath with substantially no net concurrent. oxidation of desirable metalpresent, such as chromium.

The manner in which this invention may be essentially practicedcomprises carrying it out in an electric furnace lhaving a hearth and ahollow electrode or electrodes adapted to have charges or burdens ofcomminuted reagent forming material, preferably formed into briquettesor cores, forced through the electrode toward the arc end thereof. Inthe hollow electrode a reducing reaction is caused to take place undercontrolled conditions for forming a highly concentrated reagent havingas its essential components a reduced metal and a metal-oxide uniformlydispersed or dissolved therein. On the furnace hearth there is chargedthe metallic material or metal alloy to be rened where it is melted intoa molten mass or bath whose essential components are a slag, anda metalcontaining one or more oxidizable impurities ('such as carbon sulphur,silicon, phosphorus, or manganese, or possible combinations thereof)desired to be removed from the metallic material of the molten bath. Thereagent which is in liquid form and ls hotter than the molten bath dropsrepetitively to the bath where the miscibility of -the liquid reagentand the molten bath permits a rapid and extensive dispersion of thereagent throughout the bath. This dispersion results in the oxide of thereagent being reduced by the carbon or other oxidizable impurity insolution in the bath of metal or alloy to be refined. The reduction ofthe oxide frees the metal of the oxide to be added as increments thereofas metal to the 'molten alloy and the oxidation of the oxidizableimpurities converts them into a gas, for instance carbon into carbonmonoxide, and oxides such as SiO@ MnO, etc., which may enter the slag.This carbon monoxide gas and the carbon monoxide from the hollowelectrode are evolved to such an extent that a super-atmosphericpressure is attained in the furnace for keeping out of the furnace anyair. These stepsor reactions can be carried on continuously orrepetitively for even though an intensely reducing reaction is takingplace in the electrode, and anintensely oxidizing reaction is takingplace in the bath on the hearth, and both of these zones are in onefurnace, they are independently situated and each is outv of the rangeof inuence of the other. Correctives may be supplied to and used in thebath on the hearth for changing its reactive characteristics or forassuring the permeability of the slag to the reagent discharging intothe bath from the arc end of the electrode. The refined metal orreconstituted alloy is recovered by separating it from its slag in theusual manner. Alloys are readily made by this process because the oxidesof diierent metals can be fed to the electrode, or various metals can bemelted on the hearth.

:l The formation of the reagent comprising mes -j t'allic oxideuniformly dispersed in metal is effectbeen disseminated into the metalor has gonen.

into solution in the metal: third, controlling the mobility orflowability of the coacting charge in the electrode so that the morefluid coactive material thereof as it becomes molten does not ow awayfrom the unmelted material with which it is desired to have the meltedmaterial coact,

' or to discharge from the electrode until the desired disseminating orsaturation of the reduced metal with the oxides takes place. Thiscontrol is effected by feeding to the electrode along with the otherstarting materials certain substances called herein correctives. Variouscorrectives can be used for this purpose and they may be used either toretard the mobility of the reacting mass within the electrode, or toaccelerate it, as the case may be. In the embodiment of the inventionshown and described herein, the oxidizing reagent is used for refining abath of metal on the hearth of the same electric furnace wherein thereagent is formed, but it is possible to form the liquid reagent in onefurnace, solidify it by cooling (preferably rapidly) and then use it forrefining metal in another furnace by supplying the reagent to the moltenbath of metal to be going will be set forth in the followingdescription. In the accompanying drawings there has been illustrated thebest embodiment of the invention known at present, but such embodimentis to be regarded as typical only of many possible embodiments, and theinvention is not to be limited thereto. In the drawings, Figure 1 showsdiagrammatically how the invention may be carried out essentially. Fig.2 is`a vertical sectional view of a more preferred form of furnace forcarrying out this'invention. Fig. 3 shows a vertical sectional viewtaken along the line 3--3 in Fig. 2.

Fig. 1 is self-explanatory and is intended t0 make visually identiablethe various features described herein. In the arrangement shown morecompletely in Figs. 2 and 3, I0 represents the furnace, having a top II,side walls I2 and a hearth I3 made of suitable refractory material,

the nature of which will vary according to the use to which it isdesired to put the furnace. The furnace is desirably heated by means ofelectrical energy and to this end there is provided an electrode orelectrodes Ill which project through the side walls of the furnace in asubstantially horizontal position, although the position of theelectrodes may be changed. The electrodes are desirably formed with anaxial passage or bore therethrough so that the electrode is hollow andthereby is adapted to receive and permit passage therethrough at apredetermined rate of charges or cores or cartridges C of predeterminedcomposition; under predetermined heat conditions; and surrounded by anatmosphere of predetermined nature.

The arc section of the hollow interior or bore I5 of the electrode formsa reaction chamber or reagent forming zone as the electrode itselfconstitutes an electric furnace since the arc can be used to heat thearc section of the electrode to reaction temperatures. Thereagent-forming raw material is preferably in molded form such as coresC and these cores are fed to the electrode` individually. Forautomatically feeding these cores to the electrode, one after anotherthere is in existencean apparatus which carries out that function. Pairsof abutting electrodes are preferably used which may be of any desiredcomposition such as graphite, carbon, or other suit able refractorymaterial, for thus ecaciously providing the heating and reductionchamber or zone wherein the reagent of this invention is formed. Amolten oxidizing material constituting the reagent I I dropping from theelectrode is collected on the hearth I3 of the furnace. I6 indicates themolten bath of metallic material or alloy to be rened or reconstitutedwhich is on the hearth I3 and this constitutes the refining zone of thisinvention. This bath is made up of metal or metallic material I8 havingoxidizable impurities such as carbon therein, and slag I9. 20 indicatesthe furnace tap-hole, 2| indicates a draw-olf oi flue which may be used,if necessary, for conducting gases from the furnace, although it is.normal to maintain a super-pressure in the furnace.

The components of one o1' a group of cores C forcibly supplied to theelectrode I4 comprise the reagent-forming materials including reactablereagents, correctives, and a binder for holding the components in coreform. The reactable reagents include oxides of one or more metals (whichmay lbe in the form of ore containing gangue material); and a reducingagent composed of one or more such reagents as carbon, carbonaceousmaterial, silicon, silicon-carbide or the like, the correctives arehereinafter described in detail.

As the charge is forced through the electrode and the heated zonethereof is encountered, the materialsof the charge while confinedtherein and exposed to a sufficiently high temperature undergo twochanges, namely, a chemical reaction takes place between thatpredetermined amount of reducing agent present and as much of the oxidepresent as nds its chemical requirement in the reducing agent. That is,it is arranged in advance so that there will be only enough reducingagent present toreduce a portion of the oxide to metal, leaving aquantity of the oxide unreduced. The reaction products are reduced metaland an oxide. Also a physical change occurs, namely, the chemicallyformed metal fuses or melts and subsequently as increased temperaturesare encountered lying above aovaisc the melting point of the reducedmetal' the metal becomes an active solvent in which the unreduced oxidedissolves. After reaction between the reducing 'agent and the oxide hasoccurred, increments of metal are formed or released from the oxide andlarger amounts of both oxide and reducing agent will dissolve. So withthis in mind, the oxides selected for the reagent forming material fedto the electrode are chosen by considering whether or not theseincrements of metal released from the oxide to the bath are to be of thesame metal or metals of the bath or diierent ones. Oxides usable forAthis purpose either alone or in combination are those oxides which arereducible by carbon such as manganese oxide,

' hromium oxide, iron oxide, silicon oxide and the ire. As the charge isin an openended electrode,

that part of the charge which melts first tends to run out of theelectrode, or at least to iiow away from the place of its liquefaction.To overcome this, the presence of 'a corrective material in the chargeis effective when it has the property of controlling, such as eitherretarding or accelerating as the case may be, the rate of flow of theentire mass. If the corrective is for conning or holding in place thecomponents of the mass having lower melting points, as the temperatureof the mass is increased, there is no escape of they been realized andthe entire mass becomes iluid.

of 3MnO+SiO,+6C practically lno Such a corrective for this purpose mightbe called an antifiux, and include magnesia, lime. clay, aluminum-oxide,comminuted slag from previous runs, or mixtures of such slags. If thecorrective is used for accelerating the mobility of the mass, itsfunction is to maintain the relative positions of the reduced metal andthe residue from the cores until a predetermined .temperature isreached, whereupon the mass, as a whole', flows from the electrode.These maybe termed iluxes and may consistv of silica, calcium silicate,iiuorspar; slags,` etc.

For instance, if a unitary charge were made up reduction would takeplace because the MnO.SiO, has such a low melting point that themanganese silicate would iiow out from the hollow electrode at atemperature below which neither the MnO or the S10, can bereduced withcarbon.4 Thus, the tem-- perature at which the mass flows may precludelthe reduction of the oxide. However, if one core is fed to the reactionzone made up of 3MnO+4C MnC+3CQ andthen if another `core is fed to thereaction zone made up of Si0,+2C- Si}-*2CO, the reduction takes place asindicated because the temperature at which the mass flows is highrenough to induce reduction of the metal oxide with the carbon. Or,conversely, where highly infusible material is present in the reactionzone, a ux can be added which by lowering the melting point of therefractory material will tend topermit the mass to flow instead ofpermitting selective flowing of the dierent materials. I

This tendency of some materials to melt and flow prematurely can beanticipated by analyzing the ingredients of the charge and referring tomelting points of its various components and their combinations as givenin the International Critical Tables. VFrom these tables it can be de?termined readily what ingredient to add and what quantity thereof isnecessary to control to the quantity thereof to metal.

desired gure the melting or rather the flow point of the mass as awhole.

The melting of the reduced metal is insufficient to cause the metaloxide to dissolve therein. The temperature of the molten metal must beraised above its melting point to increase the solubility function or'characteristics thereof to a point where the metal oxide is solubletherein, which is done bythe use of a corrective which controls thepoint at which the mass in the electrode becomes iiuid and thus detainsthe molten metal in the heated zone of the electrode until itstemperature is raised high enough to permit the metal oxide to dissolvetherein, whereupon the liquid mass escapes or ilows from the electrode.

The melting point of the metal to be formed in the electrode is known.It is known that at this temperature, the solvent action of the metalfor the oxide is substantially zero. Therefore, depending upon the rateand/or temperature at which the desired reduction and dissolution is totake place. is determined what corrective materials are to be used andfed to the electrode in the cores of starting material. The minimumtemperature to which the mass in the electrode must be raised is abovethat at which carbon or other reducing agent reacts with the otherreactive materials such as the oxides to reduce'a The optimumtemiperature depends upon the melting point of the metal or alloy beingreduced from the metal oxide material and the rate at which dissolutionof the oxide in the metal is desired to take place.

It is difficult to state definite temperatures in view of the manyvariables. It is a case of trial and error because it is impossible toknow. precisely what temperature is being attained inthe electrode, thetest beingwhether or not the mass rate of feed of the cores is varieduntil liquid only drops or discharges vfrom the electrode. In general,`the optimum temperature is approximately Anot less than 3200 F. and maygo to 3600D F. or even above.

The solubility of the metal oxide in the reduced metal solvent varies atdierent temperatures. So the extent of solubility is the function of thedifference between the melting point of the metal and the temperature atwhich the metal acts as or exhibits characteristics of a solvent.Usuallya temperature of from 400 to 600 F. above the melting point ofthe reduced metal, orr alloy of metals, is required to have the metalfunction satisfactorily as a solvent for the metal-oxide present in theelectrode or reagent zone. The fact that this' temperature is usuallywell below the melting point of the metal-oxide is an indication thatthe oxide does go into solution rather than into suspension, althoughthe uniform dispersion and the formation of the needle-like crystals inthe chilled or quickly cooled reagent makes it quite clear that solutionhas taken place, as was determined in the case of chromium alloys andchromium oxide.

Another phase of operation that is to be controlled is the uniform speedof passage of the reactive materials through the hollow electrode. Thatis,` it is desirable to use a constant linear speed of the chargethrough the electrode. Also it becomes necessary to pass a constantweight of starting materials per minute through the electrode. Yet asthe cores used contain various components having different specificgravities, it becomes desirable to change or lessen the Weight of itymay be used. A simple method is to use saw` dust as a source of carbonfor the reduction reaction as this also lessens the specific gravity ofthe charge.

So .from the reaction or reagent forming zone of the electrode, there isobtained a highly concentrated reagent formed under conditions favorableto dissolving substantial amounts of metal oxides therein, which reagentcomprises a metaloxide or mixtures of metal oxides in solution in areduced metal or in a mixture of reduced metals in liquid form, and thisreagent is prepared exteriorly of the bath I8. It comprises an oxidizingreagent formed while actually reducing metal and when solidified may besold as an article of commerce to such users thereof as alloy makers orrefiners. This reagent I'I is then ready to be used in the refiningoperation in the rening zone I3. In the refining zone, or hearth I3,there has been previously charged the metal or alloyed metal to berefined, and melted into a bath IIS, which bath consists essentially ofthe metal or metallic material to be refined and an oxidizable impuritysuch as carbon, or impurities which are to be removed from the metal.This involves the physical action of melting the metal to a point whereits `impurity or undesirable constituent such as carbon goes intoliquefaction or solution therein. As can be seen from Fig. 1, thereagent drops a little at a time but continuously from the electrodeinto this bath. Each drop is believed to comprise a globule of metalsurrounded by slag. The reagent and the bath of metal to 'be refinedbeing liquid and miscible permit a rapid and extensive dispersion of thereagent in the bath which results in a molten mixture of metal-oxide,metal, and carbon. Upon this mixing, a chemical reaction takes placebetween the carbon of the bath and the oxide of the reagent by virtue ofwhich there is formed carbon-monoxide and additional metal. As theelectrodes become very hot in the forming therein of the active reagentand the produced reagent is at a very high temperature (usually from.400 F. to 600 F. above the vtemperature of themolten metal of thebath), a violent reaction occurs when the reagent enters the molten bathcausing terric turbulence when the carbon monoxide is liberated by thereaction. This turbulence increases the surface contact between thereacting materials. With low carbons, almost all of the carbon reductioncan be accounted for through a reaction with the reagent emanating fromthe electrodes. Thus there is effected in the rening zone,

an intensely oxidizing action. This refining action results in therearranging or reconstituting of the metal or a metal alloy of the bathto decrease the carbon content thereof. The slag coming into therefining zone with the reagent from the electrode and any -slag I9rising from the bath I6 floats and the resulting refined metal I8 can bereadily separated therefrom by known means.

The significance of this rening step may be explained by showing thatfor the molten bathv of alloy to be rened on the hearth by treatmentwith the reagent from the electrode: there can be used scrap or wastemetal having an excess of an impurity or undesirable element thereinwhich is oxidizable such as carbon and the like, because the refiningreagent having some reducible material therein, in being mingled inliquid phase with the bath having an oxidizable element produces areaction that oxidizes the undesirable element or impurity which in itscombined form with oxygen escapes from the metal mixture. If the thusproduced oxide is not a gas but of the type of Si0 P20., and MnO, it maybecome a component of the slag. If it is a gas of the type of CO, itbecomes a part of the atmosphere of the furnace. Such gas, together withthe gas generated in the electrode causes a super-atmospheric pressureof substantially pure carbon monoxide in the furnace, and this pressurecauses gas leaving the furnace to permeate through the electrode burdenand out from the hollow electrode in a direction opposite to that of thecore feed. There is substantially no nitrogen and carbon-dioxide in theatmosphere in the furnace.

con or carbon by the use of iron oxide (FeO) in the reagent. Carbon canbe decreased in quantity in alloys of iron and manganese by a reagentcomposed of an iron-manganese alloy having manganese-oxide in solutiontherein.

v In a furnace embodying this invention, electrodes were used that where8" in diameter which had a bore of 3%". The cores used were from 2% to3" in diameter and either 81/2" or 17" long. The cores were fed throughthe electrode, depending upon the furnace temperature and the materialof the cores, at speeds ranging from 2" to 8" per minute. 'I'he 81/2cores weighed from 3 to 4% pounds depending upon the material from whichthey are made. The reagent forming zone in this furnace was found to bein the electrodes Within ten inches from the arc end thereof.

The oxidizing reagent of this invention may be made in one furnace andused elsewhere in a refining furnace. In such an event, the reagent mustobviously be cooled to solidication so it can be transported from theplace of its formation to the place of its use so this inventioncontemplates such a solidified electric furnace product as an article ofcommerce. If the reagent of this invention is solidified, it is foundtocomprise essentially a metal having uniformly dispersed therein crystalsof an oxide of one of the alloyed metals. If a quantity of this reagentis chilled or cooled quickly, the crystals of chromium oxide are foundto be needle-like and disposed in the metal in parallel formation oreach oriented in the same direction. If however the reagent is cooledslowly the crystals are found to be of varying concentration ornon-uniformly distributed inthe metal.

As can be seen from Figs. 1 and 2, the reagent formed in the reactionzone drips or drops into the bath, but in order to get into the bath,the drops of reagent II must pass through or penetrate the iioatingoxidizing slag I9. To that end this slag must be maintained in acondition to permit such penetration, for otherwise the slag may be toothick or too rigid or viscous for the free flow of the dropstherethrough. Retarda- So, by using4 the control taught by thisinvention, there can tion of the contact or mixing of the reagent drops7:

with the metal of the fbath tends to*I produce .a harmful change oftemperature and of the constitution of the reagent. That is, this delayin its travel from the electrode outlet to the metal bath may cause achange in the equilibrium in vet the reagent and a disturbance in thevalue of the metallic components thereof.

Another requirement of the slag is that it shall contain an oxide toinsure against the harmful strippingy or removal of the metal oxide fromthe reagent as it passes through the sl-ag. Accordingly, corescontaining correctives for the slag of the bath to correct the physicalconstants and chemical properties thereof may be either fed through theelectrode or added directly to the bath on the furnace hearth. Suchcorrectives include cores either in whole or in part of lime, magnesia,burned dolomite, silica, magnesium silicates, calcium silicates, sodiumsilicate, nuorspar, feldspar, salts, slags from previous runs, and anymixtures of these correctives, one essential compound being an oxide ofa metal, such as iron, manganese or chromium, since it is necessary tohave an oxide vi' a metal for oxidizing the carbon.

In connection with the use of these correctives,

it is pointed out that the reaction in the reagent forming zone mayrequire a basic slag while the refining reaction may require an acidslag or vice versa. Therefore, it is possible that one core used forfurnishing ferro-chrome to the bath may furnish it with an acid slagwhile an alternate core may keep alkaline the slag on the bath. For

instance, in order to get a good lyield of ferrochrome from the ore, itis necessary to add sufiicient silica to certain ores to increase themobility of the mixture in the electrode to release the such as chromite(chromium oxide) and carbon are started through the electrodes to insureat reducing atmosphere ln the furnaces. This prevents the oxidation ofany of the values in the charge. So, as soon as CO is generated in thefurnace, the metal charge of cold scrap, or other metallic material tobe rened, is then added to the furnace hearth. This scrap may be in theform of discarded ingots which failed to meet customers specifications,or in the form of refuse such as strip trimmings, punchings, turnings,etc. The temperature of the furnace and its electrodes is regulated bycurrent input. The rate of core' feed is regulated 'so that the desiredreducing and dissolving actions take place in the electrode whereby nonon-fluid material issues therefrom, andcores continue to. be fed untilthe scrap ris entirely melted.

Samples of the slag and molten metal are taken from the bath on thehearth at stated intervals, such as every minutes to determine thecondition of the rened metal. For instance in makand the chrome has beenraised to the desired.

point. If the carbon has not been reduced sureached the desiredanalysis, it is tapped into a ladle and is allowed to cool until it hasreached a pouring temperature. It is then poured into molds either foringots or for other purposes. After the material has been cast, theelectrodes are partially withdrawn from the furnace and a new charge ofscrap is added; the electrodes again put in place and the current turnedon and the above described steps are repeated.

For making chrome alloys it should be considered that chrome ore iscomposed of two com- 'ponents The primary component is the mineralchromite which comprises approximately 80% to 90% of 4the ore and hasthe following formula:-

In this component the molecular sum of the bases (A+B) is always equalto the molecular sum of the acids (C-l-D). A portion of this componentcan be reduced at a definite temperature by such reducing agents ascarbon or silicon.

The second component of the chrome ore (usually termed the gangue)comprises approximately-% to 10% of the oreand consists of (MgO)X(SiO,)y. lThe proportions of magnesium oxide and silicon dioxide vary betweenthe formulas and (Siog- This second component is not reduced by reducingagents such as carbon or silicon under usual conditions.

Whenthe first component is partially reduced to metal by the process ofthis invention, the iron oxide of the base and the chromium oxide (Caos)of the acid of lthe primary component are reduced forming an alloy ofmetallic iron and metallic chromium while in the residual material ofthe primary component the magnesium oxide and aluminum oxide react andcombine with the secondarycomponent magnesium silicate to form spineland magnesium-aluminum silicate. The spinel, which consists of magnesiumalumi- K nate, hasa particularly high melting point, and,

If, however, the melting point is not sufficiently..

high for the reaction and equilibrium which is required in the reagentin the hollow electrode, it is'then possible to add to the electrode ascorrectives either magnesium oxide or calcium oxide to increase therefractoriness or melting point of -this residual material, Upon theaddition of magnesla'or lime the residual material, after the reductionof the iron oxide and chromium to metal, will have a melting point inaccordance with predetermined calculations.

At least a part of then carbon in the metal is removed by the reagentformed in the electrode. Probably the percentage of carbon removed bythe slag to the percentage removed by the reagent varies inversely withthe percentage of carbon in the metallic bath on the furnace hearth. Inother words, when the carbon in the metallic bath is relatively high,there is an appreciable reaction between the oxides in the slag and thecarbon in the metal. This reaction is a function of the surface contactbetween the slag and the metal. This surface'contact is increased to agreat extent bythe turbulence caused when the dissolved metal-oxides inthe reagent drop into the metallic bath and through reaction with thecarbon therein, evolve CO.v With low carbons almost all of the carbondecrease can be accounted for through a reaction between the carbon andthe reagent emanating from the electrodes.

In considering the reactions between oxides and metals in the bath,` itmust be borne in mind that the order of the reactions between the oxidesand the metals varies with the temperature. Silicon and manganese aremore easily removed by oxidation than carbon when the temperature of thealloy is slightly above the melting point. At higher temperatures, it ismore difficult to remove silicon and manganese than carbon. At lowtemperatures FeO will oxidize metallic chromium from the metal,converting it into Cr,O, which goes into the slag without materiallychanging the carbon content of the bath. At higher temperatures, theratio of chromium to carbon removed by FeO favors lthe carbon removal.

The recovery of materials which cannot be comminuted economically suchas stainless steels of varying composition can be effected by meltingthe materials on the hearth of the furnace and correcting this wastematerial to a predetermined specification as to desirable constituentssuch as chromium and nickel, and undesirable constituents such as carbonby feeding the cores of proper material through the electrode.

Ercample 1.-'10 make low carbon ferro-manganese three methods may beusedz-l. The low carbon ferro-manganese can be produced by feeding asreagent-forming materials to the electrode cores containing manganeseore, carbon and the proper corrective. The initial material formed inthe refining zone will contain carbon in appreciable quantities but asthe refining action .progresses and the metal bath increases in mass dueto increments thereto of metal released from the reagent as the oxidethereof is reduced to metal by oxidation of the carbon of the bath, thecarbon content of the bath will obviously-decrease to an exceedingly lowpoint.l This method requires considerable tima-2. In a furnace vof thetype described a charge of high carbon ferromanganese is charged throughthe door into the hot furnace. Before the metal is charged cores havebeen fed through the electrodes until the furnace atmosphere is composedof carbon monoxide. This prevents the oxidation of the manganese. If ahigh manganese product is-desired then cores composed of manganese ore,carbon and corrective material such as lime or magnesia are.sup plied tothe electrode until the resulting reagentI from the electrode causes thecarbon of the bath to be decreased to the desired point-3; Slags rich inmanganese or manganese ore may be melted in the hearth or refining zoneof the furnace. Cores composed of SiOy with a theoretical amount ofcarbon are fed to the electrode to form a reagent containing siliconmetal. The silicon of the reagent reduces the manganese in the slag ofthe bath` on the hearth to a metallic manganese. A metal substantiallyfree from silicon carbon may be obtained if this reaction is stopped atthe point where all the manganese is reduced from the slag but noincrements of silicon from the reagent have been added to the metal. IfSilico-manganese is to be made the silica-carbon cores are fed to theelectrode until the desired percentage of silicon is obtained in the`molten metal on the hearth.

Example II-Stainless steels.-1000 lbs. of stainless steel are chargedinto the heated hearth of the furnace. Power is admitted through thehollow electrode until the charge partially melts. Cores made fromchrome ore and the theoretical amount of carbon calculated to bringabout a partial reductionof the metallic oxides are fed through theelectrodes at the rate of 21/2 per minute until sufcient reagent fromthe electrodes has caused the chromium content of the bath to reach apredetermined percentage. At this point the carbon is probably reducedto the predetermined percentage. If a furnace sample taken from the bathshows that the carbon is not suiliciently reduced, but that the chromiumis high enough, iron oxide cores which have the theoretical amount ofcarbon are supplied to the electrode at the proper rate until theresulting reagent has caused the carbon to be reduced to thepredetermined figure.

In this example it is sometimes necessary, depending upon thecomposition of the chromium ore from which the cores are made, to addenough silica to the core mixture so that the melting point of theresidual gangue in the electrode will be about 3200" F. This can beaccomplished by consulting any of the standard melting point curvesfound in the critical tables. This melting point is not the propermelting point for the slag floating on the metal in the bath and forthat reason cores containing silica (SiO,) can be fed to the electrodealternately with the chrome ore cores at a set ratio, whereby themelting point of the slag on the bath can be corrected to apredetermined figuren this case 2850 F. to 2900o F. Although this silicamay be added through the door of the furnace, it is preferable to add itthrough the hollow electrode so that a permeable slag condition will bemaintained on the surface of the metal.

Example IIL- Another example for the preparation of stainless steel isto use 1000 lbs. of steel scrap, preferably with low phosphorus content,without paying any attention to inclusions of oxides, sulphur or siliconcontent, and melting the scrap on the hearth of the furnace. Corescontaining chrome ore and the theoretical percenta'ge of carbon for thereduction of the metal-4 lic oxides are fed to the electrodes forcausing the oxidizing reagent to drop onto the hearth and into themelted steel scrap until the chrome content of the bath has reached thedesired proportion due to increments of chromium to the bath from thereagent and from reaction between the reagent and the carbon of thebath. At this point, if any nickel is to be added, it

may be added through the door of the furnace or by cores through theelectrode. When this method for the preparation of stainless steel is.

with careful control of'other impurities in accordance with thespecifications of the ilnished product, and insuilicient'carbon toreduce all of the metallic oxide contained inthe ore fed to theelectrode. The cores are added to the electrode until the reagenttherefrom oxidizes the carbon of the molten scrap until the carboncontent has reached the predetermined allowable percentage. Carbon-freeiron can also be made by supplying such cores to the electrode andomitting f rom the hearth any starting scrap as the reagent itself-fromthe electrode will form the reiined metal .on the hearth.

Specifically then, this invention is directed to .the treatment with anovel highly concentrated oxidizing reagent of intermediatemetallurgical products, such as pig iron, ferro-silicon, cast iron,high-carbon ferrochrome, high-carbon fer --romanganese, siliconmanganese, silicon chromium, and any metallurgical products containing apercentage of either alone or in combination of carbon, silicon, sulfur,phosphorus, and the like oxidizable impurities or undesirableconstituents. l

ln this invention the advantages of the undesired presence of thesereducing agents in the intermediate metallurgical products is utilizedfor the reduction of the oxide of the novel reagent by which themetallic alloy is substantially rid of its impurities. l

This patent issues from a patent application which constituted acontinuation in part of patent application Ser. No. '724,024 led May 5,1934 which ln turn was a continuation in part of patent application Ser.No. 597,399 filed March 7, 1932.

li claim:

1. In thereiining of a metal-bearing material made up of a plurality ofconstituents including at least one metal as a desirable constituentthereof and at least one oxidizable undesirable constituent thereof, theprocess for modifying the proportion of certain constituents thereofwhich comprises forming a molten bath of the material to be refined andan oxidizing slag thereon in a carbon monoxide atmosphere, forming anoxidizing reagent composed essentially of metallic oxide and a reducedmetall at a temperature in excess of the melting point of the reducedmetal while conned in a substantially horizontal hollow electrode,supplying a quantity of reagent to the bath for liquid admixturetherewith under conditions for inducing an oxidizing action of thereagent upon the oxidizable undesirable constituent of the molten bathby virtue of which the proportion thereof is decreased throughconversion into an omde, and then recovering rened metallic materialfrom the bath.

2. 'I'he process according to claim 1 in which the proportion of thedesirable constituent of the metal-bearing material to be refined isincreased by supplying an oxide of that constituent as a component ofthe reagent-forming mixture in the electrode by virtue of reactiontaking place in the bath whereby the oxidizable undesirable constitVuent of the bath reduces this oxide to release the reduced metal thereofinto the bath.

3. The process according to claim 1 in which the material to be refinedmay contain as the desirable constituent thereof at least one of theelements chromium, iron, manganese, and silicon.

4. The process according to claim l in which the material to he refinedmay contain as the undesirable constituent thereof at least one of theelements carbon, manganese, and silicon.

5. The process according to claim 1 in which the reagent is a metallicoxide dissolved in metal` 6. 'Ihe process according to claim l in whichthe reagent is supplied to the molten bath while at a temperatureranging substantially between 400 F. and 600 F. above the temperature ofthe bath.

7. The process according to claim 1 with the addition of supplying asubstance to the bath to make the slag thereof. readily permeable bysaid reagent whereby the reagent can pass through the slag and come incontact with Ithe liquid thereunder without substantial change ofcomposition of the reagent.

8. The process of refining metal alloys containing chromium as desirablemetal and an oxidizable undesirable constituent such as carbon whichcomprises dropping from a hollow electrode into a molten bath of thealloy to be rened drops of a liquid reagent containing essentially anoxide of the chromium and a reduced metal, under such conditions that areaction takes place between the reagent and the molten bath whereby theoxidizable undesirable constituent such as carbon is oxidized andincrements of the chromium of the oxide are released into the bath, andrecovering the rened and reconstituted alloy from the bath.

9. The metallurgical process which comprises forming a molten bath ofmetal material to be rened and an oxidizing slag thereon in a carbonmonoxide atmosphere, forming an oxidizing agent of metal and a metaloxide heated while held in dispersed contact to a temperature above themelting point of the metal and below the melting point of the oxide,supplying a quantity of the oxidizing agent to the bath for liquidadmixture therewith for inducing an oxidizing action of the agent uponoxidizable impurities in the bath, and then recovering the treated metalfrom the bath.

' GILBERT E. SEIL..

ies

